Science, Tech, Math › Animals & Nature Overview of Thylacosmilus Share Flipboard Email Print American Museum of Natural History Animals & Nature Dinosaurs Prehistoric Mammals Basics Paleontologists Carnivores Dinosaurs & Birds Herbivores Marine Reptiles Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated May 29, 2019 Name: Thylacosmilus (Greek for "pouched sabre"); pronounced THIGH-lah-coe-SMILE-us Habitat: Woodlands of South America Historical Epoch: Miocene-Pliocene (10 million to 2 million years ago) Size and Weight: About six feet long and 500 pounds Diet: Meat Distinguishing Characteristics: Short legs; large, pointed canines About Thylacosmilus The "saber-toothed" mammal plan has been favored by evolution more than once: Killer fangs didn't develop only in the large placental mammals of the Miocene and Pliocene epochs, but in prehistoric marsupials as well. Exhibit A is the South American Thylacosmilus, the huge canines of which apparently kept growing throughout its life and were kept tucked in pouches of skin on its lower jaw. Like modern kangaroos, Thylacosmilus raised its young in pouches, and its parental skills may have been more developed than those of its saber-toothed relatives to the north. This genus went extinct when South America was colonized by the "true" mammalian saber-toothed cats, exemplified by Smilodon, starting about two million years ago. (A recent study has found that Thylacosmilus possessed an embarrassingly weak bite for its size, chomping down on its prey with the force of an average house cat!) By this point, you may be wondering: how is it that the marsupial Thylacosmilus lived in South America rather than Australia, where the vast majority of all modern marsupials reside? The fact is, marsupials evolved tens of millions of years ago in Asia (one of the earliest known genera being Sinodelphys), and spread to various continents, including South America, before making Australia their favored habitat. In fact, Australia had its own version of a large, catlike carnivore, the similar-sounding Thylacoleo, which was only distantly related to the line of pseudo-saber-toothed cats occupied by Thylacosmilus.